1. Field of the Invention
The present invention relates to a trial for sizing replacement prosthesis for a portion of a bone. More particularly, the present invention relates to a modular trial for determining the size of a replacement prosthesis for a limb of the body.
2. Description of the Prior Art
Various prostheses have been designed to replace a portion of a bone joint. Generally a head portion is connected to an arm composed of a neck and a stem or shaft that will be embedded in the medullary canal of a bone for reconstruction. Such prostheses are often formed with an integral stem and neck portion, often a removable head element is positioned on the proximal end of the neck.
Recently modular structures fitted together from a number of replaceable parts that are available in a variety of sizes have been used. Using such prostheses it is possible to replace either the head portion or trochanteral portion of the prostheses, or both portions without removing the stem from the bone cavity. U.S. Pat. Nos. 4,676,797, and 4,693,724 are illustrative of such devices.
A disadvantage of the prostheses mentioned above is they limit the surgeon""s ability to simply and quickly assemble the proper prosthesis components during a surgery and require using the actual prosthesis components for sizing, thus risking sterility of the prosthesis components.
According to the present invention a modular trial instrument having opposed ends for sizing of an implantable orthopedic prosthesis is provided. The instrument comprises a head component located at one end of the trial and having at least one connection portion and a stem component located at the other end of the trial defining a longitudinal axis. The stem component includes a tip portion and a connection portion longitudinally opposed from the tip portion. The tip portion of stem component is received in the medullary canal of a bone.
One advantage of the present invention is the trial preferably consists of components of various lengths and sizes that are adapted to be assembled together to form a custom trial for a prosthesis of a desired length and size. One advantage of this feature is that a trial of a desired length and size may be assembled at the during of the operation.
Another advantage of the present invention is the trial can be quickly and easily assembled and disassembled without the expenditure of special forces and the use of any tools.
Another advantage of the present invention is a modular trial is provided that allows a surgeon a great deal of flexibility as to the length and size of the trial.
Another advantage of the present invention is a surgeon may easily assemble a custom trial in the operating room before the prosthesis is inserted into the patient.
Yet another advantage of the present invention is a modular trial is provided that individual components can be assembled and disassembled, the prosthesis need not be rotated in screwing movements or the like, allowing the trial to be easily used in confined areas.
The modular trial of the present invention thus provides the ability to assemble and disassemble a number of components to produce a custom trial prosthesis by selecting different lengths and sizes of individual components to meet the requirements of the individual patient exactly.